| 摘要 |
A well work-over drilling rig uses a single cylindrical column forming a mast for assembly and disassembly of a casing, pipe or rod forming a well string in a well bore. The mast supports a hydraulic ram for elevating a crown block having arms radially extending equal distances from the axis of the ram. Cables are supported by sheaves at the outer ends of the arms to permit equal and opposite forces (moments) to be applied to the column by the weight of pipe sections or the complete well string. The column is stabilized by racking pipe sections, including up to the full length of a well string, annularly around the column mast on a rotatable fingerboard, with substantially the full weight of pipe sections on the lower annular support. This avoids the need for lateral guy wires to stabilize the column mast.
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